As is known, handheld printers afford mobile convenience to users. Unlike their immobile or stationary counterparts, users determine the navigation path of a given swath of printing. In some instances, this includes random movement over a media. In others, it includes back-and-forth movement attempting to simulate a stationary printer. Regardless, successful handheld printing dictates that image information relative to the printer location be available at all times. However, all users do not navigate in the same fashion. Nor do they navigate at the same speed or housing orientation. For at least these reasons, handheld printers rely heavily on sensor inputs, such as those from optical sensors or encoders, for printing images. Yet, sensor inputs are sometimes limited in their capabilities and print jobs are interrupted due to lost or inaccurate printer location calculations.
If the printer location ever becomes lost, the printer can either quit printing or guess at location. If printing quits, users have incomplete print jobs. If locations are guessed, print quality suffers. In either, poor results are obtained. In the event printer locations are not completely lost, but simply inaccurate, print quality suffers because of inappropriately placed ink print patterns being deposited on the media. Error accumulation also adds to the problem of ink placement.
To overcome this, certain prior art has suggested sensors that identify typographic structures on the media to determine position of the printhead relative to the paper. This has shortcomings, however, for want of positioning assistance in areas or regions of the media where no typographic structures exist.
In other art, optical sensors are employed to correlate current locations to previous locations to find a delta between the locations. Appreciating typical optical sensors have numerous data pixels, correlation becomes computationally extensive because comparisons of large amounts of pixel data to other large amounts of pixel data require large storage and processing power. Because the sensors also sample fairly rapidly, the volume of pixel data increases quickly thereby requiring correlation techniques to have relatively fast processing times.
Accordingly, there exists a need in the art for robust, multi-directional and random printing handheld printers having improved print quality. Particularly, there are needs by which handheld printers are able to ascertain position regardless of particularized media area or regions. The need further extends to processing of sensor signals with less computational complexity while still remaining fast and powerful. Naturally, any improvements should further contemplate good engineering practices, such as relative inexpensiveness, stability, flexibility, ease of manufacturing, etc.